Inhibition of silvering in photographic processing solutions

ABSTRACT

Orthomercaptobenzoic acid provides good antisludgant action in photographic processing solutions. It is effective in inhibiting silvering or sludging in monobaths, especially in monobaths having high silver halide solvent activity. These include socalled thiosulfate monobaths.

United States Patent Grant Milford Haist;

David Alan Pupo, both of Rochester, N.Y. [21] Appl. No. 888,809

[22] Filed Dec. 29, 1969 [45] Patented Oct. 26, 1971 [73] Assignee Eastman Kodak Company Rochester, N.Y.

Continuation-impart of application Ser. No. 505,967, Nov. 1, 1965, now abandoned.

[72] Inventors [54] INHIBITION OF SILVERING IN PHOTOGRAPI-IIC Field of Search ..96/6 1 61 M [56] References Cited UNITED STATES PATENTS 2,377,375 6/1945 Russell 96/109 3,519,427 7/1970 Sutherns 96/109 OTHER REFERENCES Photographic Science and Engineering, Vol. 5, No. 4, July- Aug. 1961, pp. 198- 203 Primary Examiner-Norman G. Torchin Assistant Examiner-Mary F. Kelley Attorneys-W. H. J. Kline, B. D. Wiese and R. E. Knapp ABSTRACT: Orthomercaptobenzoic acid provides good antisludgant action in photographic processing solutions. It is effective in inhibiting silvering or sludging in monobaths, especially in monobaths having high silver halide solvent activity. These include so-called thiosulfate monobaths.

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to photographic processing solutions and methods. In one of its aspects it relates to a method of preventing darkening and the formation of precipitates, e.g. sludge, in processing compositions, especially in processing compositions which exhibit both developing action and fixing action on photographic silver halide materials. In another of its aspects it relates to photographic processing compositions, especially monobaths, which are resistant to silvering or sludging.

2. Description of the State of the Art So-called developer-fixer compositions, also known as monobaths, for processing of photographic silver halide materials have been known for many years. Monobaths containing a combination of developing agents with silver halide complexing agents greatly simplify the mechanics of processing photographic elements. Developing and fixing take place in a single solution. Typical monobaths are set out in U.S. Pat. No. 2,875,048 of Haist et al. issued Feb. 24, 1959; U.S. Pat. No. 3,173,789 ofKing et al. issued Mar. 16, 1965; an article by Marilyn Levy in Photographic Science and Engineering, Volume 2, No. 3 (1958) pages 136-141; and an article by GM. Haist, J.R. King and Lil. Bassage in Photographic Science and Engineering, Volume 5, No. 4, Jul-Aug. 1961, pages 198-203.

The differences between a silver halide developer solution and a monobath are well known. Hereinafter, the term monobath is intended to include all photographic processing solutions which have a silver halide solvent activity equal to that of an aqueous solution containing at least 5 grams per liter of sodium thiosulfate. The silver halide solvent activity of such a processing solution can be much higher, such as in the case of a monobath containing 50 grams per liter or more of sodium thiosulfate. Monobath solutions which are useful in socalled diffusion transfer systems or processes usually have a level of silver halide solvent activity which is equal to that of an aqueous solution containing between 5 grams per liter and 50 grams per liter of sodium thiosulfate, i.e., and intermediate level of silver halide solvent activity. In diffusion transfer systems silver halide in unexposed and undeveloped areas of a photographic silver halide element is complexed with a silver halide solvent, eg sodium thiosulfate, and transferred to a socalled receiver sheet where it is reduced or deposited on appropriate development nuclei. The fixing capacity, i.e., the silver halide solvent activity, of a processing solution need not be as great as the fixing capacity of a monobath which is not to be employed in a diffusion transfer system.

One difficulty which arises in the use of monobaths, especially those which have the described level of silver halide solvent activity, is the tendency of the monobath to darken and sludge as soon as some silver ion is present in the solution. This takes place when strips of photographic silver halide film are processed in such a monobath. Silver complexes formed from the silver halide in the unexposed and undeveloped areas of the photographic element by silver halide solvent action of the fixing agent generally are not stable in' the presence of silver halide developing agents commonly employed. Some reduction takes place in solution to form colloidal silver. As the concentration of this silver in the solution increases, the solution tends to darken, scum can form and sedimentation or sludge can form or be deposited. This is undesirable in the solution because it can cause undesired results to the photographic elements processed, e.g., stain and spots. This is especially undesirable in processing solutions in processing apparatus, especially at high temperatures. The sludge can deposit on parts of the equipment employed for processing,

such as rollers, belts, etc., as a scale which can clog orifices or scratch film.

One method of avoiding deposition of so-called silver sludge has been to use an agent other than a thiosulfate, such as certain thio compounds, as a fixing agent. However, it has been found that nonthiosulfate fixing agents tend to lose their activity after an undesirably short time due to aerial oxidation. Further disadvantages are often present in the undesirable odor of certain mercapto compounds.

A number of processes have been proposed to simplify or avoid these problems. For example, U.S. Pat. No. 2,453,346 of Russell issued Nov. 9, 1948, discloses the use of various sulfur compounds in conjunction with metal salts for stabilizing silver prints. Acidic solutions containing the sulfur compounds and metal salts are applied to silver halide emulsion layers following development of the silver image. In U.S. Pat. No. 2,525,532 of Dreywood issued Oct. 10, 1950, emulsion layers are developed with a p-methylaminophenol hydroquinone silver halide developer solution containing various sulfur compounds. Following development, the emulsions are treated with acid solutions prior to drying. Regarding monobaths, U.S. Pat. No. 3,255,008 of Tefft issued June 7, 1966, discloses a monobath containing thioglycollic acid (mercaptoacetic acid), beta-mercaptopropionic acid, mercaptosuccinic acid, and 3-mercapto-l,2-propanediol. U.S. Pat. No. 3,252,787 of Kazen issued May 24, 1966 discloses the use of thiomalic or mercaptosuccinic acid in a monobath. Also, while mercaptosuccinic acid, mercaptoacetic acid, and cysteine have been employed as fixing agents in monobaths, as described by G. M. I-laist, J.R. King and L.H. Bassage in Photographic Science and Engineering, Volume 5, No. 4, Jul-Aug. 1961, pages 198-203, none of these has been effective as an antisludging agent in photographic processing solutions, especially in monobaths. This is demonstrated in the following comparative examples.

Orthomercaptobenzoic acid has been employed as an antifoggant in photographic developer solutions as described, for example, in U.S. Pat. No. 2,377,375 of Russell issued June 5, 1945. The concentrations of orthomercaptobenzoic acid which are effective for antifoggant purposes are described as between 0.01 and 1.0 gram per liter of developing solution. The present invention is concerned with processing solutions with the described level of silver halide solvent activity and with a concentration of an antisludgant which effectively retards sludging without undesired sensitometric effects on the photographic element processed.

There are many kinds of antifoggants similar to orthomercaptobenzoic acid useful for hindering or preventing formation of fog in silver halide emulsion layers, but such compounds are not in general effective antisludgants in monobaths.

In the case of most heterocyclic antifoggants, their solubility in aqueous solutions is low. For example, most triazoles, tetrazoles and oxazoles can be dissolved in monobath solutions to only a very small extent, which limits their effectiveness to prevent sludging. Also the tendency of such antifoggants to form a strong bond with silver, which makes them good antifoggants, limits the concentration of such compounds which can be present during silver halide development. This is due to the fact that reduction of exposed silver halide grains is inhibited when antifoggants are absorbed on the grains. Accordingly undesired sensitometric characteristics result when such compounds are employed in higher than antifoggant concentrations. In many cases the antifoggant can prevent desired fixation with thiosulfate, Further, many antifoggants are ineffective in preventing or hindering sludging as demonstrated in the following comparative examples.

Accordingly, there has been a continuing need to provide an effective means for reducing or preventing sludging in photographic processing solutions having the described silver halide solvent activity, especially in a monobath, without undesired sensitometric effects on a photographic element processed in such a processing solution.

SUMMARY OF THE lNVENTiON it has been found according to the invention that reduced sludging, without undesired sensitometric effects on a photographic element process, is provided in a liquid photographic processing solution or process employing orthomercaptobenzoic acid in a photographic processing solution having appreciable silver halide solvent activity, especially in monobaths.

According to the invention, orthomercaptobenzoic acid is employed in antisludgant concentrations in monobaths which include those processing solutions which have a silver halide solvent activity equal to that of a photographic processing solution containing at least grams per liter of sodium thiosulfate, especially those processing solutions containing at least about 80 grams per liter of sodium thiosulfate. A concentration of 2 to grams of orthomercaptobenzoic acid per liter of processing solution as described is effective to provide antisludgant activity.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Accordingly one embodiment of the invention is in a monobath comprising a silver halide developing agent, a fixing agent and an antisludgant, the improvement comprising an antisludgant concentration of orthomercaptobenzoic acid as the antisludgant. The monobath as described comprises 2 to 10 grams of orthomercaptobenzoic acid per liter of the monobath to provide antisludgant activity.

The usefulness of orthomercaptobenzoic acid as an antisludgant in the described processing solutions is not limited to a particular type of silver halide developing agent or silver halide fixing agent. Any of the well-known silver halide developing agents of the phenol or aminophenol type as well as pyrazolidone silver halide developing agents can be employed. Typical of pyrazolidone silver halide developing agents useful in monobath compositions of the invention are set out in British Pat. 930,572, including l-phenyl-3- pyrazolidone, 1-phenyl-4,4-dimethyl-3-pyrazolidone, l-phenyl-5-methyl-3-pyrazolidone, l-phenyl-4-methyl-3- pyrazolidone, l,5-diphenyl-3-pyrazolidone, l-para-tolyl-3- pyrazolidone, l-phenyl-2-acetyl-4,4-dimethyl-3-pyrazolidone (the acetyl group hydrolyzes off to yield active developing agent), l-para-hydroxyphenyl-4,4-dimethyl-3-pyrazolidone, l-(2-benzothiazolyl)-3-pyrazolidone, lphenyl-4-methyl-4- hydroxymethyl-3-pyrazolidone and 3-acetoxy-l-phenyl-3- pyrazolidone. These 3-pyrazolidone silver halide developing agents are particularly useful and they can be incorporated partly or wholly within the photographic element processed. However, for rapid monobath processing, it is desirable generally to have sufficient pyrazolidone silver halide developing agent in the aqueous developing solution. Other blackand-white photographic silver halide developing agents which can be employed alone or in combination with the described 3-pyrazolidone silver halide developing agents include, for example, polyhydroxybenzenes, such as hydroquinone silver halide developing agents, e.g. hydroquinone, alkyl substituted hydroquinone, such as tertiary butyl hydroquinone, methyl hydroquinone, dimethyl hydroquinone; catechol and pyrogallol; chloro substituted hydroquinones, such as chloro hydroquinone or dichloro hydroquinone; alkoxy substituted hydroquinone, such as methoxy or ethoxy hydroquinone; aminophenol developing agents, such as N-methyl-paraaminophenol and 2,4-diaminophenols; ascorbic acid developing agents such as ascorbic acid and ascorbic acid ketals; and the like. The concentration of developing agent in the processing solution according to the invention can be varied depending on several factors such as the particular components of the processing solution, the photographic element processed, desired image, processing conditions and the like. One or more of the described silver halide developing agents can be incorporated directly into the photographic material 7 The described photographic processing solutions employed in the practice of the invention, especially monobath compositions, can comprise any of the conventional water-soluble fixing agents, typically thiosulfate fixing agents, such as sodium thiosulfate, potassium thiosulfate and lithium thiosulfate,.ammonium thiosulfate and the like. The concentration of the described fixing agent can be varied, but it is important to have the concentration sufficiently high to fix or stabilize the desired concentration of the unexposed silver halide present in the photographic element. As described, the processing solutions employed in the practice of the invention have high silver halide solvent activity, i.e., equal to an aqueous solution containing at least 5 grams per liter of sodium thiosulfate, preferably at least grams of sodium thiosulfate per liter of monobath. The maximum concentration of fixing agent, especially sodium thiosulfate, is primarily a function of the concentration of the silver halide in the emulsion process. Frequently, concentrations as high as grams of thiosulfate per liter of monobath composition can be employed and good quality prints can be produced in 5 seconds or less using such compositions. If the concentration of photographic silver halide in the emulsion is increased, then it is possible that concentrations of thiosulfate in excess of 160 grams per liter can be employed. Overfixing is, of course, to be avoided.

While sodium thiosulfate is the preferred silver halide solvent employed in the practice of the invention, other silver halide solvents can be employed in the described processing solutions such as ammonium thiosulfate, tetraalkyl ammonium thiosulfate, ammonium thiocyanate, ammonia, organic amines, urea, thiourea, and substituted thioureas such as thiosinarnine. Concentrated solutions of sodium sulfite can sometimes be suitable, depending on the total salt concentration and solubility of the components of the described processing solution.

The concentration of orthomercaptobenzoic acid required to provide the desired antisludgant activity without undesired sensitometric effects is dependent upon the nature of the processing solution to which the orthomercaptobenzoic acid is added, upon the processing conditions such as temperature, upon exhaustion conditions of the processing solution, and other factors. Photographic processing solutions which have a silver halide solvency activity toward the lower described range will require a lower concentration of antisludging agent. A concentration of 2.0 to 10.0 grams of orthomercaptobenzoic acid per liter of processing solution is suitable. In a so-called thiosulfate monobath employed at about 20 C., the concentration of 2.0 to 5.0 grams of orthomercaptobenzoic acid is preferred.

Typical processing solutions, especially monobaths, employed in the practice of the invention are aqueous solutions. However, other solvents can be employed if desired, or can be employed in combination with water. For instance, it can be suitable to employ organic solvents such as an organic amine and/or hydroxyl amine solvents, e.g. propylamine, butylamine, Z-aminoethanol, 2-methylaminoethanol, 2- ethylaminoethanol, diethanolamine (2,2-iminodiethanol), 2- aminopropanol, morpholine, and the like. Such organic solvents can have other effects than solvent action such as providing development activation.

Any silver halide development activator and any suitable concentration of development activator can be employed in the described processing solutions which provides the desired alkalinity or pH to provide the desired development. Typical development activators include inorganic development activators such as sodium hydroxide, potassium hydroxide, lithium hydroxide, sodium carbonate, and potassium carbonate as well as organic activators, such as organic amines, e.g. hydroxyalkyl amines, such as ethanolamine, morpholine, propanolamine and the like. The pH of the processing solutions employed in the practice, can vary over wide ranges but in general a pH of at least 9 and preferably about 10 to about 13 is employed.

A preferred embodiment of the invention is a monobath comprising at least 80 grams of sodium thiosulfate per liter of the monobath as a fixing agent and 2 to grams of orthomercaptobenzoic acid per liter of the monobath as an antisludgant.

An example of a monobath suitable in the practice of the invention comprises an aqueous solution containing about 4 grams of 3-pyrazolidone silver halide developing agent, about 12 grams of a hydroquinone silver halide developing agent, about 50 grams of sodium sulfite, about 110 grams of sodium thiosulfate pentahydrate, about 4 grams of sodium hydroxide and 2 to 10 grams of orthomercaptobenzoic acid per liter of the monobath.

Another embodiment of the invention is in a method of preventing sludging in a monobath by the addition of an antisludging agent to the monobath, the improvement comprising employing as the antisludgant 2 to 10 grams of orthomercaptobenzoic acid per liter of the monobath. Preferably the monobath comprises at least 80 grams of sodium thiosulfate per liter of monobath.

The processing solutions employed in the practice of the invention can contain a hardener, especially a glutaraldehyde bis (sodium bisulfite). Other hardeners which can be employed in processing solutions are suitable in the practice of the invention.

Processing according to the practice of the invention can be carried out under various conditions, usually ambient conditions such as about 20 to about 30 C. at atmospheric pressure. However, higher temperatures can be employed if desired. Particularly where rapid processing is desired, temperatures up to about 60 C. can be employed.

The time of processing employing the processing solutions and processes described can vary from about 1 second to several minutes or more depending on the desired image, processing conditions, particular components of the described processing bath, and the like.

Accordingly another embodiment of the invention is in a photographic method comprising developing and fixing an image in an exposed photographic silver halide element employing a monobath the improvement wherein the monobath comprises a silver halide developing agent, a fixing agent and an antisludgant which is orthomercaptobenzoic acid.

The compositions and processes employed in the practice of the invention are suitable for developing and fixing an image in a wide variety of photographic elements, especially photographic silver halide gelatino emulsions. The photographic element which can be developed and fixed according to the practice of the invention include those which are nonspectrally sensitized, such as X-ray emulsions or emulsions which are orthochromatic, panchromatic, infrared-sensitive and the like containing spectral sensitizing dyes. For instance, spectral sensitization can be obtained by treating the photographic silver halide emulsion with a solution of a sensitizing dye in an organic solvent or the dye can be added in the form of a dispersion. For optimum results the dye can either be added to the photographic silver halide emulsion as a final step or at some earlier stage. Spectral sensitizers which can be used include the cyanines, merocyanines, complex (tri or tetranuclear) merocyanines, complex (tri or tetranuclear) cyanines, holopolar cyanines, styryls, hemicyanines, e.g., enamine hemicyanines, oxonols, and hemioxonols.

The described photographic elements employed in the practice of the invention contain a photographic salt, especially a photographic silver salt. Suitable photographic silver salts include silver chloride, silver bromide, silver bromoiodide, silver chlorobromoiodide or mixtures thereof. The photographic silver halide can be coarse or fine grain and the emulsion containing the photographic silver halide can be prepared by any of the well-known procedures in the photographic art, such as single-jet emulsions, double-jet emulsions, such as Lippmann emulsions, ammoniacal emulsions, thiocyanate or thioether ripened emulsions, such as those described in U.S. Pat. No. 2,222,264 of Nietz et al. issued Nov. 14, 1940; U.S. Pat. No.

3,320,069 of lllingsworth issued May 15, 1967 and U.S. Pat. No. 3,271,157 of McBride issued Sept. 6, 1966. Surface image silver halide emulsions can be used or internal image silver halide emulsions such as those described in U.S. Pat. No. 2,592,250 of Davey at al. issued Apr. 8, 1952; U.S. Pat. No. 3,206,313 of Porter et al. issued Sept. 14, 1965; U.S. Pat. No. 3,367,778 ofBerriman et al. issued Feb. 6, 1968; and U.S. Pat. No. 3,447,927 of Bacon et al. issued June 3, 1969. If desired, mixtures of surface and internal image silver halide emulsions can be used as described in U.S. Pat. No. 2,996,382 of Luckey et al. issued Apr. 15, 1961. The silver halide emulsion can be a regular grain emulsion such as described in Klein and Moisar, Journal of Photographic Science, Volume 12, No. 5, Sept-Oct. 1964, pages 242-251.

The silver halide emulsion employed in the practice of the invention can be unwashed or washed to remove soluble salts. in the latter case the soluble salts can be removed by chill setting and bleaching or the emulsion can be coagulation washed.

The silver halide employed in the practice of the invention can be sensitized with chemical sensitizers, such as with reducing agents; silver, selenium, or tellurium compounds; gold, platinum or palladium compounds; or combinations of these. Suitable procedures are described, for example, in U.S. Pat. No. 1,623,499 of Shepard issued Apr. 5, 1927; U.S. Pat. No. 2,399,083 of Waller et al. issued Apr. 23, 1946; U. S. Pat. No. 3,297,447 of McVeigh issued Jan. 10, 1967; and U.S. Pat. No. 3,297,446 of Dunn issued Jan. 10, 1967.

Photographic silver halide emulsions employed in the practice of the invention can be protected against the production of fog and can be stabilized against loss of sensitivity during keeping. Suitable antifoggants and stabilizers, e.g., used alone or in combination include, for example, thiazolium salts; azaindenes; mercury salts as described, for example, in U.S. Pat. No. 2,728,663 of Allen et al. issued Dec. 27, 1955; urazoles; sulfocatechols; oximes described, for example, in British Pat. No. 623,448; nitron; nitroindazoles; polyvalent metal salts described, for example, in U.S. Pat. No. 2,839,405 of Jones issued June 17, 1958; platinum, palladium and gold salts described, for example, in U.S. Pat. No. 2,566,263 of Trivelli et al. issued Aug. 28, 1951 and U.S. Pat. No. 2,597,915 of Yutzy et al. issued May 27, 1952.

A photographic element or emulsion described and used in the practice of the invention can contain various colloids alone or in combination as vehicles, binding agents and in various layers. They are transparent or translucent and include both naturally occurring substances such as proteins, for example, gelatin, gelatin derivatives, cellulose derivatives, polysaccharides such as dextran, gum arabic and the like; and synthetic polymeric substances such as water-soluble polyvinyl compounds like poly(vinyl pyrrolidone), acrylamide polymers and the like. Other synthetic polymeric compounds which can be employed include dispersed vinyl compounds such as in latex form and particularly those which increase dimensional stability of photographic materials. Suitable synthetic polymers include those described in U.S. Pat. No. 3,142,586 of Nottorf issued July 28, 1964; U.S. Pat. No. 3,193,386 of White issued July 6, 1965; U.S. Pat. No. 3,062,674 of l-louck et al. issued Nov. 6, 1962; U.S. Pat. No. 3,220,844 of ll-louck et al. issued Nov. 30, 1965; U.S. Pat. No. 3,287,289 of Ream et al. issued Nov. 22, 1966; and U.S. Pat. No. 3,411,911 of Dykstra issued Nov. 19, 1968. Efiective polymers include water insoluble polymers of alkyl acrylates and methacrylates, acrylic acid, sulfoalkyl acrylates or methacrylates, and those which have cross-linking sites which facilitate hardening and curing as well as those having recurring sulfobetaine units as described in Canadian Pat. No. 774,054.

The photographic and other layers of an element employed in the practice of the invention and described herein can be coated on a wide variety of supports. Typical supports include cellulose nitrate film, cellulose ester film, poly-(vinylacetal) film, polystyrene film, poly(ethylene terephthalate) film,

polycarbonate film and related films or resinous materials, as well as glass, paper, metal and the like. Typically a flexible support is employed, especially a paper support which can be partially acetylated or coated with baryta and/or an alpha olefin polymer, particularly a polymer of an alpha olefin containing 2 to 10 carbon atoms such as polyethylene, polypropylene, ethylene-butene copolymers and the like.

The photographic and other layers of an element used in the practice of this invention can be hardened by various organic or inorganic hardeners, alone or in combination, such as aldehydes, and blocked aldehydes, ketones, carboxylic and carbonic acid derivatives, sulfonate esters, sulfonyl halides and vinyl sulfonyl ethers, active halogen compounds, epoxy compounds, aziridines, active olefins, isocyanates, carbodiimides, mixed-function hardeners and polymeric hardeners such as oxidized polysaccharides like dialdehyde starch and oxyguargum and the like.

, The photographic elements used in the practice of the invention can contain antistatic or conducting layers. Such layers can comprise soluble salts such as chlorides, nitrates and the like, evaporated metal layers, ionic polymers such as those described in U.S. Pat. No. 2,861,056 of Minsk issued Nov. 18, 1958 and U.S. Pat. No. 3,206,312 of Sterman et al. issued Sept. 14, 1965 or insoluble inorganic salts such as those described in U.S. Pat. No. 3,428,451 of Trevoy issued Feb. 18, 1969.

The photographic layers or other layers employed in the practice of the invention can contain plasticizers and lubricants. Suitable plasticizers and lubricants include, for example, polyalcohols such as glycerin and diols described, for example, in U.S. Pat. No. 2,960,404 of Milton et al. issued Nov. 1, 1966; fatty acids or esters such as those described in U.S. Pat. No. 2,588,765 of Robijns issued Mar. 11, 1952; U.S. Pat. No. 3,121,060 of Duane issued Feb. 11, 1964; and silicone resins such as those described in British Pat. No. 955,061.

The photographic layers or other layers employed in the practice of the invention can contain surfactants such as saponin; anionic compounds such as alkyl aryl sulfonates described, for example, in U.S. Pat. No. 2,600,831 of lBaldsiefen issued June 17, 1962; amphoteric compounds such as those described in U.S. Pat. No. 3,133,816 of Ben-Ezra issued May. 19, 1964; and adducts of glycidol and an alkyl phenol such as those described in British Pat. No. 1,022,878.

If desired, the photographic elements employed in the practice of the invention can contain matting agents such as starch, titanium dioxide, zinc oxide, silica, polymeric beads including beads described, for example, in US. Pat. No. 2,922,101 of Jelley et al. issued July 11, 1961 and U.S. Pat. No. 2,701,245 of Lynn issued Feb. 1 1955.

The photographic elements employed in the practice of the invention can contain brightening agents including stilbenes, triazines, oxazoles and coumarin brightening agents. Watersoluble brightening agents can be used such as those described in German Pat. No. 972,067 and U.S. Pat. No. 2,933,390 of McFall et al. issued Apr. 19, 1960 or dispersions of brighteners can be used such as those described in German Pat. No. 1,150,274; U.S. Pat. No. 3,406,070 of Oetiker et al. issued Oct. 15, 1968 and French Pat. No. 1,530,244.

The various layers including the photographic layers of an element employed in the practice of the invention can contain light-absorbing materials and filter dyes such as those described in U.S. Pat. No. 3,253,921 of Sawdey issued May 31, 1966; U.S. Pat. No. 2,274,782 of Gaspar issued Mar. 3, 1942; U.S. Pat. No. 2,527,583 of Silberstein et al. issued Oct. 31, 1950; and U.S. Pat. No. 2,956,583 of VanCampen issued Oct. 18, 1960. If desired, the dyes can be mordanted, for example, as described in U.S. Pat. No. 3,282,699 of Jones et al. issued Nov. 1, 1966.

The photographic layers used in the practice of the invention can be coated by various coating procedures including dip coating, airknife coating, curtain coating or extrusion coating using hoppers such as described in U.S. Pat. No. 2,681,294 of Beguin issued June 15, 1954. If desired, two or EXAMPLE 1 The following examples illustrates a monobath solution containing ortho-mercaptobenzoic acid.

A monobath having the following composition is prepared:

l-phenyl-B-pyrazolidone 4.0 grams Hydroquinone 12.0 grams Sodium sulfite (anhydrous) 50.0 grams Sodium thiosultate pentahydrate 1 10.0 grams Sodium hydroxide 4.0 grams Water to make 10 liter An exposed 35mm. by l2-inch strip of film containing a fine grain silver chlorobromide emulsion is processed in 500 milliliters of the above monobath for 6 minutes at 75 F then washed for 10 minutes in running water at 75 F.

The film surfaces are free of any adhering scum, but the solution becomes cloudy within 2 hours and begins to deposit a sediment. After standing 24 hours, the solution is still cloudy with considerably grayish-brown sediment in the bottom of the cylinder.

To another SOO-milliliter portion of the above monobath, there is added 2.0 grams of orthomercaptobenzoic acid. The pH of the solution is adjusted to 10.3 with sodium hydroxide. A similar piece of film is processed as above.

The film surfaces are free of any adhering scum. The used monobath solution remained clear without any discernible sludge for 16 days. And, the resulting developed and fixed image showed no undesired sensitometric effects.

EXAMPLE 2 This is a comparative example demonstrating advantages of the invention.

A monobath is prepared having the following composition:

Sodium sulfite 50.0 grams Hydroquinone 12.0 grams l-phenyl-B-pyrazolidone 4.0 grams Sodium hydroxide 4.0 grams Sodium thiosult'ate pentahydrate I 10.0 grams Glutaraldehyde bis(sodium 5.0 grams bisulfite) Water to 1.0 liter The pH of the monobath is adjusted to 10.2 by the addition of sodium hydroxide. One l2-inch by 35mm. strip of exposed film having a high-speed, fine-grain silver chlorobromide emulsion layer is developed and fixed for 6 minutes at about 20 C. in 500 milliliters of the described monobath. The monobath is clear and colorless before the film is processed. The clear and colorless monobath becomes hazy immediately after processing the film. Within 2 hours, silver sludge begins to settle to the bottom. A very heavy tan-colored sludge deposits from the hazy solution after 24 hours.

This demonstrates that in the absence of an antisludgant undesired sludging occurs in the described monobath.

EXAMPLE 3-l l The following examples are comparative examples to further illustrate the effectiveness of an antisludging agent according to the invention.

in each of examples 3-1 1 the following procedure is carried out, 0.01 Mols at a compound listed in table 1 is dissolved in 5 milliliters of aqueous sodium hydroxide solution containing percent by weight sodium hydroxide. This solution is then added to a SOD-milliliter portion of a monobath having the following composition:

Sodium sulfite 50.0 grams Hydroquinone l2.0 grams l-phenyl-S-pyrazolidone 4.0 grams Sodium hydroxide 4.0 grams Sodium thiosulfate pentahydrate 1 10.0 grams Water to 1.0 liter The pH of the resulting monobath is adjusted to 10.3, if necessary with a few drops of an aqueous sodium hydroxide solution containing 50 percent by weight sodium hydroxide. One 12- inch 35mm. strip of exposed film having a high-speed, finegrain silver chlorobromide emulsion layer is developed and fixed for 6 minutes at about 20 C. in 500 milliliters of the resulting monobath. Intermittent agitation, i.e., raising and lowering the film strip once each minute, is used. The film strips are then washed in water at about 20 C. for minutes and dried in air at ambient temperature. Visual observations of the condition of the monobath is made before processing the film strip, immediately afterwards, and after 24 hours. The condition of the monobath is given in the following table I for each of the noted compounds. In each instance the compounds of examples 3 through ll fail to provide desired antisludging activity and/or provide undesired sensitometric properties.

Step 20 Step l0 Step 5 Step I Moncbath A 0.20 1.57 (no orthomercaptobenzoic acid) Monobath B (0.3 g.ll. orthomercaptobenzoic acid) Monobath C (3.0 g./l. orthomercaptobenzoic acid) As indicated by the above data, 0.3 gram per liter orthomercaptobenzoic acid was effective in removing fog density in the low exposure portion of the sensitometric curve without depressing the densities in the areas of higher exposure. Higher concentrations of the compound reduce all the densities but adjustment of the monobath activity will still result in a beneficial reduction of the fog density with the added benefit of retardation of formation of sludge.

TABLE I Example Condition of Monobath Condition of Monobath Condition of Monobath Number Compound Before Processing Immediately After Processing 24 Hours After Processing 3 para-mercaptobenzoic acid... clear, colorless. clear. slight pink color. hazy. faint yellow color. 4 thiobenzoic acid. slight haze. pale yellow slight haze, yellow-tan hazy, yellow-brown color.

color. slight precipitation.

5 5,5-thiodisalicylic acid clear. very pale straw color 6 orthodoluenethiol clear. colorless...

7 L-cysteine hydrochloride clear. colorless color. slight precipitation. clear. slight pink color.

.. clear. bright yellow color.

much yellow sludge. hazy, light yellow-brown much dark brown sludge. hazy. straw color. much gray-tan sludge. cloudy. bright yellow color.

much yellow sludge. hazy yellow-brown color.

. color. much dark brown sludge. 8 Z-drethylamrnoethanethiol colorless hazy. light tan colorv some hazy. brown color. much dark hydrochloride. settling. brown sludge. 9 l-monothioglycerol clear. colorless slight haze. tan color hazy. gray color. much black sludge.

l0 mercaptoacetic acid clear, colorless hazy. yellow tan color hazy. brown color. much dark brown sludge. slight plating.

1] thiourea clear. colorless clear. slight pink color clear. colorless. much gray-tan sludge. some plating.

*After 6 days the monobath has much deep red sludge.

EXAMPLE 12 The invention has been described in detail with particular Sludge formation in monobaths containing hardening agents such as glutaraldehyde bis(sodium bisulfite) can also be retarded by the presence of orthomercaptobenzoic acid Such monobaths often produce high fog levels in addition to showing considerable sludging after use. The data below illustrate the beneficial results of orthomercaptobenzoic acid in a hardening monobath.

The following monobaths are prepared Water to make reference to preferred embodiments thereof, but it is understood that variations and modifications can be effected within the spirit and scope of the invention.

We claim.

1 In a monobath comprising a silver halide developing agent. a thiocyanate or thiosulfate fixing agent and an antisludgant, the improvement comprising an antisludgant concentration of orthomercaptobenzoic acid as said antisludgant.

2. A monobath as in claim 1 comprising 2 to 10 grams of orthomercaptobenzoic acid per liter of said monobath as said antisludgant.

3. A monobath as in claim 1 comprising at least 5 grams of a water-soluble thiosulfate per liter of said monobath as said fixing agent.

4. A monobath as in claim 1 comprising at least grams of sodium thiosulfate per liter of said monobath as said fixing agent and 2 to 10 grams of orthomercaptobenzoic acid per liter of said monobath as said antisludgant.

5. A monobath as in claim 1 comprising a glutaraldehyde bis(sodium bisulfite) hardener.

6. A monobath as in claim 1 comprising a 3-pyrazolidone silver halide developing agent, sodium sulfite, at least 5 grams of sodium thiosulfate per liter of said monobath. sodium hydroxide, and 2 to grams of orthomercaptobenzoic acid per liter of said monobath.

7. A monobath as in claim 1 comprising an aqueous solution containing about 4 grams of 3-pyrazolidone silver halide developing agent, about 12 grams of a hydroquinone silver halide developing agent, about 50 grams of sodium sulfite, about 1 10 grams of sodium thiosulfate pentahydrate, about 4 grams of sodium hydroxide, and 2 to 10 grams of orthomercaptobenzoic acid per liter of said monobath.

8. In a photographic method comprising developing and fixing an image in an exposed photographic silver halide element employing a monobath comprising a silver halide developing agent, a thiocyanate or thiosulfate fixing agent and an antisludgant, the improvement wherein said antisludgant is orthomercaptobenzoic acid.

hardener.

11. A photographic method as in claim 8 wherein said monobath comprises about 4 grams of a 3-pyrazolidone silver halide developing agent, about 12 grams of a hydroquinone silver halide developing agent, about 50 grams of sodium sulfite, about grams of sodium thiosulfate pentahydrate, about 4 grams of sodium hydroxide and about 2 to 10 grams of orthomercaptobenzoic acid per liter of said monobath. 

2. A monobath as in claim 1 comprising 2 to 10 grams of orthomercaptobenzoic acid per liter of said monobath as said antisludgant.
 3. A monobath as in claim 1 comprising at least 5 grams of a water-soluble thiosulfate per liter of said monobath as said fixing agent.
 4. A monobath as in claim 1 comprising at least 80 grams of sodium thiosulfate per liter of said monobath as said fixing agent and 2 to 10 grams of orthomercaptobenzoic acid per liter of said monobath as said antisludgant.
 5. A monobath as in claim 1 comprising a glutaraldehyde bis(sodium bisulfite) hardener.
 6. A monobath as in claim 1 comprising a 3-pyrazolidone silver halide developing agent, sodium sulfite, at least 5 grams of sodium thiosulfate per liter of said monobath, sodium hydroxide, and 2 to 10 grams of orthomercaptobenzoic acid per liter of said monobath.
 7. A monobath as in claim 1 comprising an aqueous solution containing about 4 grams of 3-pyrazolidone silver halide developing agent, about 12 grams of a hydroquinone silver halide developing agent, about 50 grams of sodium sulfite, about 110 grams of sodium thiosulfate pentahydrate, about 4 grams of sodium hydroxide, and 2 to 10 grams of orthomercaptobenzoic acid per liter of said monobath.
 8. In a photographic method comprising developing and fixing an image in an exposed photographic silver halide element employing a monobath comprising a silver halide developing agent, a thiocyanate or thiosulfate fixing agent and an antisludgant, the improvement wherein said antisludgant is orthomercaptobenzoic acid.
 9. A photographic method as in claim 8 wherein said monobath comprises 2 to 10 grams of orthomercaptobenzoic acid per liter of said monobath.
 10. A photographic method as in claim 8 wherein said monobath comprises a glutaraldehyde bis(sodium bisulfite) hardener.
 11. A photographic method as in claim 8 wherein said monobath comprises about 4 grams of a 3-pyrazolidone silver halide developing agent, about 12 grams of a hydroquinone silver halide developing agent, about 50 grams of sodium sulfite, about 110 grams of sodium thiosulfate pentahydrate, about 4 grams of sodium hydroxide and about 2 to 10 grams of orthomercaptobenzoic acid per liter of said monobath. 